Insulating bushing



Jan. 13, 1931. 4 A BURNHAM 1,788,380

INSULATING BUSHING Filed June 30, 1926 HJHIIHIII Patented Jan. 13, 1931 UNITED STATES PATENT OFFICE GEORGE A. BURNHAM, OF SAUGUS, MASSACHUSETTS, ASSIGNOR TO OONDIT ELECTRICAL MANUFACTURING CORPORATION, OF SOUTH BOSTON, MASSACHUSETTS, A CORPORA- TION or MASSACHUSETTS INSULATING BUSHING Application filed June 80, 1926. Serial No. 119,707,

This invention relates to high tension oilfilled electric insulating bushings.

One of the troubles experienced with oilfilled bushings is the difficulty of maintaining the bushings oil tight; and an.o'bject of this invention is the provisiorrof an insulating bushing wherein such joints that must be maintained oil tight are of relatively small extent and so can be madeoil tight without difiiculty.

A further object of the invention isthe.

provision of an oil-insulated conductor-unit contained within the insulating shell of the bushing comprising a conductor and an oilcontaining insulating tube which is carried by and is in effect an integral part and surrounds the major portion of the conductor and provides oiLinsulation, said unit being removable from the shell of the bushing for repairs or replacement.

A yet further object is generally to improve the construction of insulating bush- T ig. l is a side elevation partly in section of a bushing embodying the invention.

Fig. 2 is a section along line 2'2 of Fig. 1.

Fig. 3 is a side elevation partly broken out of the removable conductor-unit comprising the conductor and the oil-containing insulating tube surrounding and carried by it.

As here shown, the insulating bushing embodying this invention comprises an outer insulating shell composed of an upper tubular section 10 and a lower tubular section 12 both of which are made of some suitable insulating material as porcelain. Said bushing is adapted to be inserted through an opening 1 1 in the wall 16 of the casing of an electrical apparatus and supported by the wall in such position.

The lower insulting member 12 is provided with an open top 18 and a bottom wall 20 which is .formed with an aperture therein through which the electrical conductor or stud 22 is extended. Said lower section is disposed within the opening in the casing wall with its open top extended for a substantial distance thereabove. An attachin ring 24 is fixed by a body of cement 26 to sai insulating shell 12 a substantial distance below the top thereof and. is attached removably to the under face of the casing wall 16 by the stud bolts 28 and nuts 30. A packing washer 32 may be interposed between the ring 24 and the casing wall to provide a fluidtight sealthereat. The upper casing section 10 is provided with an open bottom which surrounds that portion of the upper end of said lower section 12 which is disposed above the casing wall. An attaching ring 34 is fixed about the lower end of said upper section 10 by cement 36 and said clamping ring is rigidly secured removably to the outer face of the casing wall 16 by said stud bolts 28 and nuts 38. A packing washer 40 may be interposed between said attaching ring 34 and the lower end of the insulating section 10 and the casing wall to provide a fluid tight seal thereat. Said upper insulating section 10 is provided with an open top 42. An annular ring 44 is fixed to said top and is provided with an upstanding neck 46 to provide the support for the axially disposed conductor 22 and its associate components.

The conductor 22 is provided with a solid insulation 48- thereon which may comprise a plurality of layers or convolutions of bakelized paper or other suitable insulating material which is tightly wound thereon and is approximately co-extensive with the height of the enclosing insulating shell. Said conductor is disposed co-axially within an insulating tube 50 which may be composed of bakelite or other suitable insulating material and is adapted to contain oil or compound whereby to provide additional insulation of the conductor. The lower end of said tube 50 is received within a cap 52 and has a fluid tight connection therewith. Said cap may be screw threaded onto said conductor 22 and secured removably thereon in a fluid tight manner. Said tube 50 is spaced from said conductor and the solid insulating body thereon to provide an oil containing space thereabout. Said tube is provided with an oil reservoir at the up er end thereof which includes a shell 54 w ich has a removable and fluid tight connection with the upper end of said tube 50. Said shell is provided with a depending annular flange 56 which loosely surrounds the neck 46 of the insulator to provide a weatherproof seal thereat. A glass tube 58 is received within said shell 54 and the ends thereof are suitably packed in a fluid tight manner. The level of oil within said glass tube may be inspectedthrough apertures 60 in said shell 54:. Said shell is closed at its upper end by a cap 62 which is screw threaded removably to the upper end of said shell. The conductor is passed loosely through the upper end of said cap and is provided with a recessed collar 64 which is disposed over and depends loosely about an upstanding neck 66 of said cap whereby to provide a water tight seal thereat. The conductor 22 with its attached oil retaining tube 50 and associated components is adapted to be received removably within the outer insulat ing shell and is secured in position by means including a nut 68 which is screw-threaded on the lower end of said conductor and bears against the bottom wall 20 in said lower insulating section.

A packing member 7 0 may be interposed between the cap 52 of said insulating tube 50 and the bottom wall 20 of the lower insulating section 12 whereby to provide an oil tight seal at the aperture in the bottom of said insulating section. Said insulating section 12 may contain oil within it to some level a which is below the open top and is above the casing wall and the attaching rings thereby to provide enhanced insulation at the region of greatest electric stress. This particular construction of the insulator is disclosed in my copending application, Serial No. 119,708, filed June 30, 1926.

The conductor 22 is fixed at its lower end only and is free to expand and contract. The insulating tube 50 also is fixed only at its lower end and is free also to expand and contract.

Since the only joint that must be maintained oil tight in the outer insulating shell is the small one in the bottom wall 20, it can be maintained oil tight without difliculty.

Said tube and conductor and oil reservoir can be removed as a unit from the insulating shell without disturbing the connections between the insulating sections and the casing wall, and can readily be repaired or replaced by a unit having diflerent characteristics, when desired, thereby adapting the insulator readily for various conditions of service.

The structure may be otherwise modified without departing from the spirit of the invention.

I claim:

1. An insulating bushing comprising an insulating shell open at the top and having a restricted opening at the bottom, a conductor extended through and beyond the top and bottom openings of said shell, an oil-retaining insulating tube surrounding and spaced from and carried by said conductor intermediate its ends, and an oil reservoir disposed above said shell under the upper end of said conductor and carried by said tube.

2. An insulating bushing comprising an insulating shell open at the top and having a restricted opening at the bottom, a conductor extended through said shell, and through the opening at the bottom thereof and having a fixed connection with said shell only at said bottom opening, an oil-containing insulating tube surounding and spaced from and carried by said conductor, and an oil reservoir disposed above said shell and carried by said tube, said oil reservoir having a sliding connection with said shell and comprising a cover for the open top thereof.

3. An insulating bushing comprising an insulating shell open at the top, a conductor disposed within said shell and extended through and having a removable fluid-tight connection with the bottom of said shell, an insulating oil-retaining tube surrounding and spaced from and carried by said conductor intermediate its ends and having a fluid-tight connection at the bottom therewith, and an oil-reservoir carried by the top of said tube above the open top of said shell and comprising a cover for the open top of said shell. I

4. An insulating bushing comprising an insulating shell open at the top, a conductor disposed within said shell and extended through and having a removable fluid-tight connection with the bottom of said shell, an insulating oil-retaining tube surrounding and spaced from andv carried by said conductor intermediate its ends and having a fluid-tight connection at the bottom therewith, and an oil reservoir carried by the top of said tube above the open top of said shell and comprising a cover for the open top of said shell, said conductor and tube being removable from said shell through the open top thereof.

5. An insulating bushing comprising an insulating shell having separate upper and lower open-ended insulating sections with the upper section overlapping the open end of and comprising a cover for the lower sec tion, a supporting member, means securing said sections in the aforesaid relation to said supporting member, a rigid unitary conductor extended through and a substantial distance beyond the ends of said shell and having a detachable fluid-tight connection with the bottom of said lower section which connection also constitutes a support for said conductor, and an oil-retaining insulating tube surrounding and carried by and spaced from said conductor intermediate its ends and having a fluid-tight connection at its lower end with-said conductor and a cover for the top of said tube, which cover is independent of said shell.

6. An insulating bushing comprising an insulating shell having separate upper and havin lower open-ended insulating sections with the upper section overlapping the open end of and comprising a cover for the lower section, a supporting member for said shell disposed a substantial distance beneath the open end of said lower section, means independently securing said sections in the aforesaid relation to said supporting member, a conductor extended through said shell and having a detachable fluid-tight connection with the bottom of said lower section, an-oil-retaining insulating tube surrounding and carried by and spaced from said conductor intermediate its ends and having a fluid-tight connection at its lower end with said conductor, and an oil reservoir disposed above and in engaging relation with said shell and having a supporting oil-tight connection with the upper end of said oil-retaining tube.

7. An insulating bushlng comprising a conduotor, an oil-retaining insulating tube surrounding and carried by and having supports at its opposite end on said conductor and extended along the major extent thereof, said conductor having both ends extended beyond the opposite ends of said tube, and insulating supporting means for said conductor and its tube comprising an intermediately jointed insulating shell enclosing said tube and providing support for said conductor at the ends opposite the ends of said tube, said shell having attaching means securing one end of said conductor in an oil tight manner in one end of said shell, the other end of said shell a sliding connection with the other end 0 said conductor.

In testimony whereof, I have signed my name to this s ecification.

EORGE A. BURNHAM. 

